What makes the difference between the natural course of a remaining type B dissection after type A repair and a primary type B aortic dissection?

OBJECTIVES: To analyse the outcome and need for intervention [surgery or thoracic endovascular aortic repair (TEVAR)] in patients after surgery for remaining type B dissection after type A repair and primary type B aortic dissection.
METHODS: Within a 10-year period, 247 patients with remaining type B after type A, and 112 patients with primary type B aortic dissection were analysed. We assessed the clinical outcome as well as the need for intervention (surgery or TEVAR) within the aortic arch and the thoracoabdominal aorta as well as risk factors.
RESULTS: The median follow-up was 23 months (interquartile range 5-52). There was a significant difference with regard to the status of the primary entry tear between patients after surgical repair of an acute type A aortic dissection and primary acute type B aortic dissection (patent vs. non-patent entry 35 vs. 83%, P < 0.001). The overall need for any kind of intervention (surgery or TEVAR) was 19%. Multivariate Cox regression analysis revealed a patent primary entry tear in patients after surgery for acute type A aortic dissection as an independent predictor for intervention (surgery or TEVAR) during follow-up [odds ratio (OR) 6.4; confidence interval (CI) 1.39-29.81, P = 0.017]. Multivariate Cox regression analysis did not reveal a patent primary entry tear in patients after acute type B aortic dissection as an independent predictor for intervention (surgery or TEVAR) during follow-up (OR 0.67; CI 0.27-1.69, P = 0.671). Finally, the thrombosis status of the false lumen was not an independent predictor for intervention (surgery or TEVAR) either in patients after surgery for acute type A aortic dissection (OR 3.46; CI 0.79-15.16, P = 0.100) or in patients after acute type B aortic dissection (OR 0.77; CI 0.31-1.93, P = 0.580).
CONCLUSIONS: A remaining type B dissection after type A repair and a primary type B aortic dissection represent two distinct pathophysiological entities with regard to late outcome. The need for any kind of intervention in the thoracoabdominal aorta is significantly higher in primary type B aortic dissections. A remaining patent primary entry tear independently predicts the need for intervention (surgery or TEVAR) in patients after surgery for acute type A aortic dissection and, thereby, remains the main target of initial therapy. The thrombosis status of the false lumen seems to be of secondary importance.